Controlled composition fluids are present in a number of widely used fluids including municipal water supplies, beverages, gasoline, intravenous (“IV”) fluids and other useful fluids. In some cases, the controlled composition fluid is not the end product of a process, but is used in the manufacturing process of other products. For example, semiconductor manufacturing processes commonly use controlled composition fluids in cleaning and etching of semiconductor wafers.
Systems for creating controlled composition fluids typically mix a number of constituent fluids according to a proscribed ratiometric combination—in other words, a recipe. In some cases, it is not the stochiometric ratio of the fluid components that is important, but some property of the fluid mixture, such as pH, viscosity, ionic strength, conductivity or other property. Rather than controlling for the preferred property, however, it is often easier to blend the fluid components to a target concentration which corresponds to the actual target property.
Typically, fluids of a particular concentration are produced in a batch mode. In a batch process, the gravimetric or volumetric ratios of component fluids are used to determine how much of each fluid is added into a mix vessel for blending. While the use of batch process allows for fairly easy control of concentration, it limits production of the blended fluid to a particular size batch. To provide additional blended fluid, more batches of the fluid must be produced. Additionally, current batch process systems have large footprints, relatively high capital costs and a high level of complexity. Examples of batch systems include ChemFlow Systems, Inc. of Addison, Ill. batch system which blends gravity fed components volumetrically, and the MassFusion™ system by BOC Edwards.
In addition to batch processes, controlled composition fluids can also be produced using continuous flow systems that mix fluids as the fluids flow to the process chamber. These systems provide for continuous production of a fluid. Currently continuous flow systems do not provide adequate control to compensate for inaccurate or changing component fluid properties such as concentration or temperature.